Cancer is a broad name given to a group of diseases where cells grow and proliferate uncontrollably. This unregulated cell division causes formation of malignant tumors which have the ability to invade nearby parts of the body. Several treatment methods are available such as surgery, chemotherapy, radiation therapy and other targeted therapies. However, most of the therapies stated above have adverse effects and need aid in rebuilding the damaged healthy tissue during therapy. Stem cells have been used traditionally for reconstruction.
Stem cells – sources
Stem cells are these incredible cells that possess the ability to differentiate into several lineages and have the self renewal capacity to produce more stem cells. Embryonic, germinal and somatic stem cells are the main types of stem cells, divided according to their source. Embryonic stem cells (ESCs) are found in the inner cell mass of an embryo. Germinal stem cells are derived from the primary germinal layers (ectoblast, entoblast). Somatic stem cells or Adult stem cells (ASCs)are found in mature tissues.
Stem cells have a potential applications in cancer therapy due to their extraordinary self renewal capacity and choice of stem cells is very crucial for efficient regeneration. ESCs are more suitable for therapeutic purposes due to their high totipotency i.e. the ability to divide and produce all types of cells in an organism. Apart from this, ESCs have an indefinite lifespan too. However, use of ESCs for therapy is hugely restricted due to the ethical issues involved. Since ESCs are obtained from 5-day old pre-implantation embryos, the extraction process poses a risk of destroying the embryo.
Adult stem cells however have lesser ethical restrictions and higher accessibility. Due these advantages ASCs are the most commonly used stem cells for therapeutic purposes. ASCs can be obtained from many sources such as umbilical cord, blood and bone.
Role of stem cells in cancer therapy
Stem cells are used in cancer treatments as immuno-reconstruction agents. At high doses chemotherapeutic agents have harmful effects such as myelotoxicity i.e. the decrease of blood cells (cells responsible for immunity, carrying oxygen and blood clotting). Hematopoietic stem cells (HSCs) are used in Hematopoietic cell transplantation to aid in recovery of bone marrow and immune cells following high dose chemotherapy.
Apart from immuno-reconstitution, stem cells may be used as delivery vehicles of anticancer agents to targets. For example stem cells with adenoviral expression vector carrying Interferon-β gene constructs are used to increase Interferon-β production at the target site.
Life span of stem cells
Life span of ASCs are a major limiting factor in usage of stem cells in clinical applications. ASCs have a relatively shorter life span due to progressive telomere shortening. Genetic manipulations of ASCs to extend their life span is a proposed approach.
Use of stem cells in cancer therapy for immuno-reconstruction is a well known role and the use of stem cells as anti cancer delivery vehicles show promising future with their lesser side effects and efficient delivery.